1. Field of the Invention
The invention is broadly in the field of treatment of radar data for radar systems on moving platforms.
2. Description of the Related Art
When a coherent radar system is mounted on a moving platform, and the platform is moving at some velocity toward stationary reflectors the phase of the coherent echo return advances 180 degrees for each ¼ wavelength of motion toward the object. Such motion produces the well-known Doppler frequency increase. If the motion is at high speed, then many wavelengths are traversed over a short time. Search radars, while scanning terrain, contain a mainlobe beam which strikes the terrain at varying angles with respect to the ground track or line of sight. Because of such varying angle and terrain configuration, and motion of the platform, mainlobe clutter, return signals from the ground and other stationary objects, gives the appearance of moving target-like objects in the field of view of the radar. Some mitigation is required to account for the mainlobe clutter, in order to avoid the return signals from the mainlobe clutter being treated as signals from moving targets.
One prior way of handling mainlobe clutter is to process the signal to make the received return signal from fixed objects appear stationary relative to the moving platform receiver itself. Multiple examples of types of such compensation for mainlobe clutter Doppler return due to radar platform motions are described in U.S. Pat. No. 3,346,859. A drawback of such compensation methods is the large of amount of computer processing power required.
It will be appreciated from the foregoing that improvements would be desirable with regard to handling mainlobe clutter in radar systems on moving platforms.